Search

Blind image quality assessment (BIQA) for authentic distortions is still a great challenge, even in today’s deep learning era. It has been widely acknowledged that local and global features are both indispensable for IQA, which play complementary roles. While combining local and global features is straightforward in traditional handcrafted feature-based IQA metrics, it is not an easy task in the deep learning framework. This is mainly due to the fact that deep neural networks typically require input images with a fixed size. Current metrics either resize the image or use local patches as input, which are problematic in that they cannot integrate local and global aspects as well as their interactions to achieve comprehensive quality evaluation. Motivated by the above facts, this paper presents a new BIQA metric for authentic distortions by aggregating local and global deep features in a Vision-Transformer framework. In the proposed metric, selective local regions and global content are simultaneously input for complementary feature extraction, and the Vision-Transformer is employed to build the relationship between different local patches and image quality. Self-attention mechanism is further adopted to explore the interaction between local and global deep features, producing the final image quality score. Extensive experiments on five authentically distorted IQA databases demonstrate that the proposed metric outperforms the state-of-the-arts in terms of both prediction performance and generalization ability.

The understanding of the molecular defensive mechanism of Echinacea purpurea (L.) Moench against polycyclic aromatic hydrocarbon (PAH) contamination plays a key role in the further improvement of phytoremediation efficiency. Here, the responses of E. purpurea to a defined mixture of phenanthrene (PHE) and pyrene (PYR) at different concentrations or a natural mixture from an oilfield site with a history of several decades were studied based on transcriptomics sequencing and widely targeted metabolomics approaches. The results showed that upon 60-day PAH exposure, the growth of E. purpurea in terms of biomass (p < 0.01) and leaf area per plant (p < 0.05) was negatively correlated with total PAH concentration and significantly reduced at high PAH level. The majority of genes were switched on and metabolites were accumulated after exposure to PHE + PYR, but a larger set of genes (3964) or metabolites (208) showed a response to a natural PAH mixture in E. purpurea. The expression of genes involved in the pathways, such as chlorophyll cycle and degradation, circadian rhythm, jasmonic acid signaling, and starch and sucrose metabolism, was remarkably regulated, enhancing the ability of E. purpurea to adapt to PAH exposure. Tightly associated with transcriptional regulation, metabolites mainly including sugars and secondary metabolites, especially those produced via the phenylpropanoid pathway, such as coumarins, flavonoids, and their derivatives, were increased to fortify the adaptation of E. purpurea to PAH contamination. These results suggest that E. purpurea has a positive defense mechanism against PAHs, which opens new avenues for the research of phytoremediation mechanism and improvement of phytoremediation efficiency via a mechanism-based strategy.

Long-range spatiotemporal correlations may play important roles in nonequilibrium surface growth process. In order to investigate the effects of long-range temporal correlation on dynamic scaling of growing surfaces, we perform extensive numerical simulations of the (1+1)- and (2+1)-dimensional Kardar-Parisi-Zhang (KPZ) growth system in the presence of temporally correlated noise, and compare our results with previous theoretical predictions and numerical simulations. We find that surface morphologies are obviously affected with long-range temporal correlations, and as the temporal correlation exponent increases, the KPZ surfaces develop gradually faceted patterns in the saturated growth regimes. Our results show that the temporal correlated KPZ system displays evidently nontrivial dynamic properties when $0, Comment: 30 pages,12 figures

Surface growth processes can be significantly affected by long-range temporal correlations. In this work, we perform extensive numerical simulations of a (1+1)- and (2+1)-dimensional ballistic deposition (BD) model driven by temporally correlated noise, which is regarded as the temporal correlated Kardar-Parisi-Zhang universality class. Our results are compared with the existing theoretical predictions and numerical simulations. When the temporal correlation exponent is above a certain threshold, BD surfaces develop gradually faceted patterns. We find that the temporal correlated BD system displays nontrivial dynamic properties, and the characteristic roughness exponents satisfy $\ensuremath{\alpha}\ensuremath{\simeq}{\ensuremath{\alpha}}_{\mathrm{loc}}l{\ensuremath{\alpha}}_{s}$ in (1+1) dimensions, which is beyond the existing dynamic scaling classifications.

The macro and micro analysis methods of the fracture mechanics are adopted to investigate the fracture mechanics problem of functionally graded materials (FGMs) with uncertain mechanical properties and an arbitrarily oriented crack. In this paper, the piecewise-exponential model and the Mori-Tanaka model are combined to solve the mixed-mode crack problem for every sample analytically. Then according to the probability theory, the mixed-mode SIFs for the samples are obtained. So the probabilistic attributes of the mixed-mode SIFs in FGMs can be obtained. As a result, the probabilistic density function of SIFs can be provided by means of the graphic method. The method based on macro and micro mechanics can be efficiently applied to carry out the related research of the influences of the crack angles and lengths on the stochastic characteristics of the mixed-mode SIFs.

Ni-Co hydroxide nanosheets (NCHs) deposition on as-oxidized Buckypaper (BP) were fabricated by a one-step electrodeposition method for sensitive stimuli-responsive sensors (temperature, mechanical deformation etc.). This NCHs/BP film exhibits a near linear relationship between normalized electrical resistance ( R / R 0 ) responses with different external conditions, such as large coefficient of linear thermal expansion (CLTE) α of 235.0 in 10 −6 /K under temperature stimuli, and linear electro-mechanical relationship with ultimate strain of 2.1% and ultimate stress of 21.0 MPa under mechanical deformation stimuli (stretching, bending and torsion), suggesting its promising applications as thermal sensors and mechanical-stimulated devices.

Due to stricter data management regulations such as General Data Protection Regulation (GDPR), traditional production mode of machine learning services is shifting to federated learning, a paradigm that allows multiple data providers to train a joint model collaboratively with their data kept locally. A key enabler for practical adoption of federated learning is how to allocate the profit earned by the joint model to each data provider. For fair profit allocation, a metric to quantity the contribution of each data provider to the joint model is essential. Shapley value is a classical concept in cooperative game theory which assigns a unique distribution (among the players) of a total surplus generated by the coalition of all players and has been used for data valuation in machine learning services. However, prior Shapley value based data valuation schemes either do not apply to federated learning or involve extra model training which leads to high cost. In this paper, given $n$ data providers with data sets $D_{1}, D_{2}$,..., $D_{n}$, a federated learning algorithm $A$ and a standard test set $T$, we propose the contribution index, a new Shapley value based metric fit for assessing the contribution of each data provider for the joint model trained by federated learning. The contribution index shares the same properties as Shapley value. However, direct calculation of the contribution index is time consuming, since a large number of joint models with different combinations of data sets are required to be trained and evaluated. To solve this problem, we propose two gradient based methods. The idea is to reconstruct approximately the models on different combinations of the data sets through the intermediate results of the training process of federated learning so as to avoid extra training. The first method reconstructs models by updating the initial global model in federated learning with the gradients in different rounds. Then it calculates the contribution index by the performance of these reconstructed models. The second method calculates contribution index in each round by updating the global model in the previous round with the gradients in the current round. Contribution indexes of multiple rounds are then added with elaborated weights to get the final result. We conduct extensive experiments on the MNIST data set in different settings. The results demonstrate that the proposed methods can approximate the exact contribution index effectively and achieve a time speed up of up to 2x-l00x compared with the exact calculation and other baselines extended from existing work.

In this article, a fracture mechanics model for functionally graded materials (FGMs) with general thermomechanical properties and collinear cracks under thermal loading is proposed. Assuming the thermomechanical properties of FGM strip to be general continuous functions of the coordinate in the thickness direction, the FGM strip is divided into a multilayered medium with the thermomechanical properties varying exponentially in each layer. Using the superposition method, the problem is reduced to a perturbation problem in which the crack surface tractions are the only external forces. Finally, the crack problem is reduced to integral equations with generalized Cauchy kernel and solved numerically. Some typical examples are discussed and the thermal stress intensity factors (TSIFs) for the collinear cracks are presented. The influences of the geometry parameters and the interaction between both collinear cracks on the TSIFs are discussed. Some important conclusions are drawn.

This article reports the results of a probabilistic study on the mixed-mode fracture problem of an internal slant crack in a functionally graded material strip. The study involves randomness description of the micro-structural attributes of functionally graded materials; the effects of the random micro-structural attributes on the macroscopic properties of functionally graded materials; analytical solutions of mode-I and mode-II stress intensity factors and analysis of its probabilistic characteristics. The influences of the randomness in micro-structural component on the statistics (e.g. the mean, the standard deviation) of the shear modulus of functionally graded materials are graphically represented. The results also reveal this research may be more meaningful on the probabilistic characteristic of stress intensity factors of functionally graded materials with the larger size slant crack.

Ni–Co hydroxide nanosheets (NCHSs) were coated on buckypaper (BP) by a facile and one-step electrodeposition method for high-performance supercapacitor electrodes. The binary metal hydroxides show great superiority over the related single hydroxides. A novel sheet-on-tube hierarchical structure with a uniform distribution of Ni–Co hydroxides on BP shows great promise in supercapacitor applications. Such hybrid electrodes exhibit a high areal capacitance of 1.5 F cm−2 (corresponding to 1725 F g−1 based on the mass of active material), high rate capability and excellent cyclic stability. Based on the hybrid electrodes, ultrathin and highly flexible asymmetric supercapacitors were fabricated. The as-prepared asymmetric device shows high capacitance (0.3 F cm−2 at a current density of 3 mA cm−2), low internal resistance (approx. 5 Ω for the whole device), excellent long-term cycle life (capacitance retention of 92% over 10 000 cycles), and high flexibility (negligible capacitance changes during large deformation), which makes it particularly well-suited for applications in next generation high-performance energy storage systems.

The prevalence of mobile Internet techniques and Online-To-Offline (O2O) business models has led the emergence of various spatial crowdsourcing (SC) platforms in our daily life. A core issue of SC is to assign real-time tasks to suitable crowd workers. Existing approaches usually focus on the matching of two types of objects, tasks and workers, or assume the static offline scenarios, where the spatio-temporal information of all the tasks and workers is known in advance. Recently, some new emerging O2O applications incur new challenges: SC platforms need to assign three types of objects, tasks, workers and workplaces, and support dynamic real-time online scenarios, where the existing solutions cannot handle. In this paper, based on the aforementioned challenges, we formally define a novel dynamic online task assignment problem, called the trichromatic online matching in real-time spatial crowdsourcing (TOM) problem, which is proven to be NP-hard. Thus, we first devise an efficient greedy online algorithm. However, the greedy algorithm can be trapped into local optimal solutions easily. We then present a threshold-based randomized algorithm that not only guarantees a tighter competitive ratio but also includes an adaptive optimization technique, which can quickly learn the optimal threshold for the randomized algorithm. Finally, we verify the effectiveness and efficiency of the proposed methods through extensive experiments on real and synthetic datasets.

We investigate the evolution of the difference in the conventional logistic map and observed complicated but interesting dynamics. Our results show that the bifurcation, the attractor and the asymptotic measure depend on initial values. The reverse bifurcation, the multiple bifurcation and other bifurcation properties obtained here are different from those of the original logistic map. Furthermore, we find that attractors form a structure which looks like a jigsaw puzzle, and the corresponding distributions related to the Feigenbaum constant are also analyzed.

These days, with the increasingly widespread employment of sensors, particularly those attached to vehicles, the collection of spatial data is becoming easier and more accurate. As a result, many relevant areas, such as spatial crowdsourcing, are gaining ever more attention. A typical spatial crowdsourcing scenario involves an employer publishing a task and some workers helping to accomplish it. However, most of previous studies have only considered the spatial information of workers and tasks, while ignoring individual variations among workers. In this paper, we consider the Software Development Team Formation (SDTF) problem, which aims to assemble a team of workers whose abilities satisfy the requirements of the task. After showing that the problem is NP-hard, we propose three greedy algorithms and a multiple-phase algorithm to approximately solve the problem. Extensive experiments are conducted on synthetic and real datasets, and the results verify the effectiveness and efficiency of our algorithms.

Nuclear containment protects nuclear island from serious accident, while its compressive bearing capacity remains the key problem to nuclear safety. With reference to one nuclear containment, the special concrete damaged plasticity model in software ABAQUS, this article systematically analyzes influencing rules of compressive bearing capacity and factors such as gravity, steel liner, prestressed tendons etc. The result shows that steel liner and prestressed tendons play key parts in deformation inhibition and the failure mode of nuclear containment, meanwhile prestressed tendons are crucial to improve the compressive bearing capacity.Copyright © 2013 by ASME

To analyze long-range temporal correlations in surface growth, we study numerically the (1 + 1)-dimensional Kardar–Parisi–Zhang (KPZ) equation driven by temporally correlated noise, and obtain the scaling exponents based on two different numerical methods. Our simulations show that the numerical results are in good agreement with the dynamic renormalization group (DRG) predictions, and are also consistent with the simulation results of the ballistic deposition (BD) model.

Dynamic stress intensity factor is investigated theoretically on two dissimilar piezoelectric media with an interfacial crack at the edge of a circular cavity subjected to time-harmonic incident anti-plane shearing in present paper. The formulations are based on the methods of Green’s function and conjunction. Dynamic stress intensity factor at the crack’s tip are obtained by solving boundary value problems with the methods of conjunction and crack-division technique. The calculating results are plotted so as to show how the frequencies of incident wave, all kinds of physical parameters of two dissimilar piezoelectric materials, applied electric loads and geometric parameters influence on the dynamic stress intensity factor (DSIF). While some of the calculating results are compared with other published documents.Copyright © 2010 by ASME

In the present work, dynamic interaction is investigated theoretically between several circular cavities near the surface in a semi-infinite piezoelectric medium subjected to time-harmonic incident anti-plane shearing. The analyses are based upon the use of complex variable and multi coordinates. Dynamic stress concentration factors at the edges of the subsurface circular cavities are obtained by solving boundary value problems with the method of orthogonal function expansion. Some numerical solutions about two interacting subsurface circular cavities in a semi-infinite piezoelectric medium are plotted so as to show how the frequencies of incident wave, the piezoelectric characteristic parameters of the material and the structural geometries influence on the dynamic stress concentration factors.Copyright © 2009 by ASME

Dynamic interaction is investigated theoretically between a circular cavity and the surface in a semi-infinite piezoelectric medium subjected to time-harmonic incident anti-plane shearing in the present paper. The formulations are based on the method of complex variable and wave function expandedness. Dynamic stress concentration factors at the edge of the circular cavity are obtained by solving boundary value problems with the method of orthogonal function expansion. The calculating results are plotted so as to show how the frequencies of incident wave, the piezoelectric characteristic parameters of the material and the structural geometries influence upon the dynamic stress concentration factors.Copyright © 2007 by ASME

In this paper, dynamic stress concentrations are studied in an infinite piezoelectric medium with a non-circular cavity under time harmonic incident anti-plane shear wave and inplane electric field. Based on complex variable and conformal mapping method, the dynamic stress concentration factors and the electric field concentration factors at the boundary of the non-circular cavity are obtained by applying the orthogonal function expansion technique. Numerical examples about an infinite piezoelectric medium with an elliptic cavity are provided with different elliptic axial length ratios, different wave numbers and different piezoelectric characteristic parameters. The calculating results show that dynamic analyses are very important to an infinite piezoelectric medium with a non-circular cavity at lower frequencies and larger piezoelectric characteristic parameters.Copyright © 2005 by ASME